Even though I shoot a lot of sports, I won't get the lens either. Admittedly I already own the 200 f/2, 300 f/2.8 and 400 f/2.8, but I shoot wider than f/4 a ton and this isn't very useful for me. In fact, for indoor volleyball and basketball I set aperture range from f/2 to f/4 with ISO safety shift on (or if I'm using the 70-200 lens, f/2.8 to f/4). I prefer the faster shutter speed in exchange for opening up wider.

However, I can definitely see the utility in this lens, and if I didn't already have the 300 and 400, I probably would use it for football and soccer, as long as they were day games or well-lit venues. My problem is that my night stuff is NOT well-lit, so to keep a fast shutter I need wider than f/4 probably.

I think this lens would be great for well-lit sports, and wildlife photography, and it'll add a ton of convenience over the longer primes.

Canon should just look at the practical and business sense here and get rid of the idea of a built in 1.4 extender. Most photographers will be perfectly happy adding their own extenders to a 200-400/4 IS as necessary. This will simplify the lens and reduce its price.

IMHO it is nice that someone at Canon took a risk and tried to come up with something new. What is not nice is trying to stick with that plan when all indicators show it is not working.

If they can release a 200-400/4 IS at $8k I think a lot of people will buy it.

Even though I shoot a lot of sports, I won't get the lens either. Admittedly I already own the 200 f/2, 300 f/2.8 and 400 f/2.8, but I shoot wider than f/4 a ton and this isn't very useful for me. In fact, for indoor volleyball and basketball I set aperture range from f/2 to f/4 with ISO safety shift on (or if I'm using the 70-200 lens, f/2.8 to f/4). I prefer the faster shutter speed in exchange for opening up wider.

However, I can definitely see the utility in this lens, and if I didn't already have the 300 and 400, I probably would use it for football and soccer, as long as they were day games or well-lit venues. My problem is that my night stuff is NOT well-lit, so to keep a fast shutter I need wider than f/4 probably.

I think this lens would be great for well-lit sports, and wildlife photography, and it'll add a ton of convenience over the longer primes.

Most of them are not very happy with the build quality of the build in TC and the image quality if you add the TC.

I have both TC´s, why should I pay extra money for a build in TC?

My personal opinion: The lens is too big and havy as a walkaround lens compared to the EF 100-400 IS. The solution with the build in TC is not amazing. For the mentioned price I prefer the normal big whites.

So even with a TC optimized just for this lens at the long end it doesn't do better than an external TC?(still must be more convenient though)

I imagine that perfectly centering the extender when swung in from the side was a decent engineering challenge.

It would also have to be user-proof such that if the user believed they had engaged the extender, that it did engage and was perfectly aligned and couldn't move on its own even when the lens was bumped around.

Why is someone paying $10k on this f4 and not getting the 400 f2.8 mk.ii ? (Unless they can afford both... )

200-400 would be a very useful zoom range to have on the sidelines of a basketball, football, soccer, baseball, etc game. That being said, 168-420mm f/4 is better (Sigma 120-300 f/2.8 + 1.4x) and a helluva lot cheaper. Will it be as sharp? No. Good enough for the online and print media who buy such images? For sure. Will it focus fast or accurately enough? That's the question.

some pros were complaining that the “bump”, or a function of the “bump” got in the way of something

Well, I've talked to a lot of pros in person, and am secretly sleeping with the head of R&D at Canon, here's the truth (I'd rate it at CR2.5):

Because the new 3D or 1DXs or whatever it is called (I hear they're having a chook-raffle to deicde the name), 44.62MP camera with "new technology inside" is going to have a 500EX-ish sized built-in flash, GPS-receiver the size of an AWACS (for when you're deep underground shooting black cats in coal mines and need to know coordinates for how the hell to get back to the surface), plus a third grip on the top of the camera (for when you know, you need those upside-down shots). All of which will interfere with the mounting and unmounting of the lens.

They can't change the 'bump' to the right hand side because you'll graze your right-hand knuckles, the left and top are out because of the giant flash, the bottom is out because of tripod-mounting issues. So instead they're working on a solution that exactly shatters the optical elements of the teleconverter into exact 1/8 pie-pieces. The 'bump' will no longer be a bump, the lens barrel will just be slightly wider all around. When you engage the teleconverter, the pie-pieces simply squeeze together to form a perfect lens element again, with a bit of fancy fluid (kind of like dissolved lens-coatings) in there to make sure there's no extra glass/air interfaces.

...The latest we’ve heard, and from a pretty knowledgeable I person is that the lens has needed a redesign in regards to the “bump” that holds the built-in 1.4 TC....

The bump is one the same side as all of the knobs as things that you want to change. For the average shooter that has their right hand on the shutter button and left hand on the lens, I can see it getting in the way as you move your hand along the lens.

Even its proximity to the on-off knob for the TC might be such that it is hard to turn the know whilst you've got your eye up to the camera because you can't really approach the knob with your hand against the lens. When you have the camera+lens down, I can see it being easier to get at the knob... but then how easy will it be to turn that knob when wearing big gloves with that bump there in the cold?

I can easily see them moving the bump to either be on top or on the other side of the lens.

the other side wont work since it will get in the way of the Dof preview button and if you have this configured to enable AI servo and there was a bump on the way to use your $10,000 + lens you would surely want to stab someone. On top makes more sense.

Also, has anyone else noticed that if this were a 7D or anything else with flash, and there were a CPL in the filter slot, it would be mighty-hard to squeeze your finger in betwixt the flash and filter to actually turn the thing?